Electric annunciator.



No. 798,236. PATBNTED AUG. 29, 1905. H. USENER. ELECTRIC ANNUNCIATOR.

APPLICATION FILED JAN.4,19U5.

3 SHEETS-SHEET l.

No. 798,236. PATBNTED AUG. 29, 1905.

H. USENER. ELECTRIC ANNUNGIATOR.

APPLICATION FILED JAN.4,1905.

3 SHEETS-SHEET Z.

N0.`798,236. PATBNTED AUG. 29, 1905. H. USENBR.

ELECTRIC ANNUNGIATOR.

APPLICATION FILED JAN.4.19 05.

3 SHEETS-SHEET 3.

UNITED STATES PATENT OFFICE.

ELECTRIC ANNUNCIATOR.

Specification of Letters Patent.

Patented Aug. 29, 1905.

Application led January 4, 1905. Serial No. 239,572.

To ttf/Z Loh/0717. it' muy concern,.-

Be it known that I, HANS UsENER, a subject of the German Emperor,residing in KieLGermany, have invented certain new and usefulImprovements in Electric Annunciators, of which the following is aspecification.

The present invention relates to electrictelegraph apparatus, and inparticular to devices for indicating at a distance the position of atransmitting lever, pointer, or the like of a machine-telegraphapparatus for transmitting command-signals on board ship, acompass-needle, a watergage, and so on. Such devices consist in generalof a transmitter and of a receiver and means for transmitting currentfrom one to the other. In the ordinary operation of the apparatus thelever or the like of the transmitter is moved by hand or automatically7into a definite position, and it is the function of the receiver toindicate this motion automatically at the distant point, so that itspointer or the like is normally7 always in a position corresponding tothe position at the time of the transmitting-lever.

The receiver of the new device consists of an instrument having twocrossed coils which are revoluble in a constant magnetic field. Thepointer is connected with the aXle of the crossed coils, and the problemis to supply to the coils such currents when the transmitting-levermoves that the pointer connected withthem moves in unison with thetransmitting-lever. This is effected by connecting with thetransmitting-lever an electrical contact, which when the saidtransmitting-lever is moved slides over the separate contacts of aresistance which is traversed by a current, so that the difference ofpotential at the terminals of the leads connected with the -receivervaries according to the differences in potential between the variouscontacts connected with the resistance.

In the accompanying drawings, Figure 1 is a diagram showing the generalarrangement of one embodiment of the present invention. Fig. 9. is adiagram illustrating the electrical connections on the transmitter. Fig.3 is a graphic representation, hereinafter fully explained, showing themanner in which the resultant of the magnetic force of the two coils ofthe receiver varies for various positions of the transmitting-lever.Fig. 4 illustrates a modification of the apparatus shown in Fig. 1, thetransmitting-lever and a few other parts being omitted. Fig. 5 is adiagram similar to Fig. 3, but corresponding to the modified form ofapparatus shown in Fig. 4. Fig. 6 is a diagram similar to Fig. 5,corresponding to another modified arrangement similar to that shown inFig. 4. Fig'. 7 is a diagram similar to Fig. 4 and shows anothermodification of the apparatus shown in Fig. 1. Fig. 8 is a diagramillustrating the manner in which the same resistances may be employedfor the variation of the currents traversing the two crossed coils ofthe receiver hereinafter described. Figs. 9 and 10 show two embodimentsof a telegraphic device according' to the present invention, by means ofwhich the positions at any given time of two transmitters situated atdifferent places can be compared with one another at a third place.

The present invention relates to a telegraph apparatus in which aninstrument consisting of two crossed coils arranged revolubly in amagnetic field serves as a receiver. This receiver is, however,connected with the transmitter in such a manner that one end of eachcoil is kept at a constant potential which is practically zero, whereasthe potentials at the other ends of both coils vary with thedisplacement of the transmitting-lever. These variable potentials areproduced in a manner which in itself is well known-viz., by thetransmitting-lever sliding over the various contacts of aresistancetraversed by a current.

Fig. 1 shows diagrammatically the arrangement of the principal parts ofone embodiment of the present invention. The current produced by thedynamo 13 flows through a resistance 1415. which is subdivided into asuitable number of sections. The points of connection of the latter areconductively connected with the contacts 16 to 35 of the transmitter.36. These contacts, with the exception of the contacts 16 and 26, areconnected together in pairs in the manner indicated by the dotted linesin Fig. 1. The contact 16 is connected electrically with the arc-shapedcontact-block 38, while the contact 26 is in a similar manner connectedwith the arc-shaped contact-block 39. 40 is a circular contactblock,which is concentric with the contactblocks 38 39 and with the pivot 41of the transmitting-lever 42. The receiver consists, essentially, of thecoil 43, which may be termed the voltmeter-coil, the coil 44, which maybe termed the counter-force coil, and the field-magnet, of which thepoles 47 48 alone are indicated. As shown in Fig. 1, these coils arecrossed and are adapted to rotate about their axis 45 in the magneticfield be- IOO IIO

tween the poles 47 48. 46 represents the armature ot the coils. Thepointer ot' the re ceiver is not shown in the drawings. It may bemounted on the axle carrying the coils 43 44. The pivot 41 iseonnectedthrough the lead 49 with one end ot' the coil 43, and thecircular contact-block 40 is connected through the lead 50 with one endot' the/coil 44. The other ends of the coils 43 44 are connectedtogether in the diagram at the point 51, this point being connected,through the lead 52, with the contact 31 of the transmitter, which isconnected with the opposite contact 21 and with the approximately middlepoint 53 of the resistance 14 15, which point 53 is at approximatelyzero potential. rlhe transmitting-lever 42, which is Jformed in the mainof insulating material, is, as shown in Fig. 2, mounted on the pivot 41,connected with one end of the coil 43. Said pivot 41 is in electricalcontact with a conducting-bar 54, which `is in electrical contact withthe sliding contact 55, arranged on the under surface of the lever nearits outer end. This sliding contact 55 is adapted to make contact withthe contacts 16 to 35 when the lever is turned. On the'under centralportion or' the lever a conducting-bar 56 is arranged provided with tworubbing contacts 57 58, the former of which is adapted to continuallymake contact with the circular contact-block 40 and the latter of whichis adapted to make contact with one or other of the arc-shapedcontact-blocks 38 39, according to the position of the lever, or to makecontact with neither of these blocks when the contact 55 of the levermakes contact with either of the contacts '16 or 26. 59 is the handlefor operating the lever.

Referring now to the various circuits shown in Fig. 1, the current fromthe dynamo divides into three parts. rlhe lirst part passes through theresistance 14 15. 1f the brush 6() be the positive brush and the brush61 the negative,this part of the current flows through the resistancefrom 14 to 15, the end 14 being at apositive potential and the end 15 ata nega tive potential. The second part ofthe current is the part whichtraverses the coil 43. -lf the contact 55 of the lever 42 stands on anyone of the contacts 16-20 or 32-35, the second part of the current flowsfrom the end 14 ofthe resistance to that particular contact with whichthe lever is making contact and thence to the 'pivot of the leverthrough the lead 49 to the coil 43, thence through the lead 52 to thepoint 53, and thence to the end 15 of the resistance. 1f the contact 55makes contact with either ot' the contacts 22-30, the second part flowsrvia 14 and 53 to the lead 52, through the latter to the point 51,thence through the coil 43 and the lead 49 to the pivot 41 and thecontact 55, thence through the particular contact which said contact 55is touching, and so to the end 15 of vthe resistance. In this lattercase it will be noticed that the current flows 52 to the point 53 andend 15.

through the coil 43 in the opposite direction to that holding good inthe former case. li' the contact 55 makes contact with either ot' thecontacts 21 or 31, the coil 43 is short-circuited and the part of thecurrent alluded to above as the second part is zero. The third part ofthe current, which is the part which traverses the coil 44, also dependsupon the position otl the lever. 1n case the lever is in such a positionthat the contact-bar 56 makes an electrical connection between thecontactblock 40 and the contact-block 39, which is arranged as shown inFig. 1, then the third part or' the current flows 'from the end 14 tothe point 53, through the lead 52 and the coil 44 and lead 50, to thecontact-block 40, and thence through the bar 56 to the contact-block 39,the contact 26, and the end 15 of the resistance. In case thecontact-bar 56 forms a connection between the contact-blocks 4() and 38the 'current in the coil 44 is reversed and tiows from the end 14 to thecontact-block 38, through the bar 56 to the contact-block 40, thencethrough the lead 50, coil 44', and lead lt' the lever makes contact witheither otl the contacts 16 or 26, the contact-block 40 is not connectedwith either ofthe blocks 38 or 39, and consequently no current flowsthrough the coil 44, the part of the current termed the third partbeing' zero.

Fig. 3 shows graphically the manner in i which the resultant of themagnetic forces due to the two coils 43 44 varies in magnitude when theposition of the transmitting-lever is changed. rlhe diagram correspondsto only one half ol the circle ot' contacts, the diagram for the otherhalt' being similar to the diagram shown. 1t moreover corresponds toapparatus similar to that shown in Fig. 1, but having one more contactin each quadrant ol the circle of contacts than that shown in saidligure. In constructing Fig. 3 it is moreover assumed that such valueshave been found, experimentally or by theory, for the various sectionsof the resistance 14 15 that when the transmitting-lever moves from oneContact to the next the resultant magnetic force moves, with regard tothe coils, through the same angle as that moved through by the lever. Itis of course understood that the resultant magnetic force is alwaysparallel to the lines ot' force ot' the magnetic field produced betweenthe poles 47 48 when the coils are at rest, the coils adjustingthemselves until this state of parallelism exists. In Fig. 3, however,as stated above, the relative directions of the resultant torce and thecoils are ,shown for various positions of the transmitting-lever. Toconstruct Fig. 3, the axes 64 65 66 and 65 67 are first drawn, the axis64 65 66 representing the trace or line of section ot' the plane of thecoil 44 with a horizontal plane and the axis 65 67 a similar trace ofthe plane of the coil 43. Then the thirteen radius-vectors, each of IlOwhich makes an angle of iifteen degrees with its neighbor, are drawn, itbeing assumed, as stated above, that the apparatus has been so designedthat at -each step the magnetic resultant moves with regard to the coilsthrough the same angle as the transmitting'- lever. Then the line 62 63is drawn parallel to the axis 64 65 66 at a distance the abscissa ofwhich corresponds to the magnetic force due to the coil 44, while thecontact-bar 56 makes contact between the contact-blocks 40 and 39. Thepoints 62 7l 70 69 68 67 72 73 74 75 63 are the points of intersectionof the line 62 63 with the radius-vectors which do not coincide with theaxis 64 65 66. As the magnetic forces due to the two coils 43 44 act atright angles to one another and as the magnetic force due to the coil 44is represented in magnitude and direction by the line 65 67, it followsat once from the proposition known as the parallelogram of forces7 thatthe magnitudes of the resultant in its various directions arerepresented by the length of the diagonals 65 62, 65 71, 65 70, 65 69,65 68, 65 67, 65 72, 65 73, 65 74, 65 75, 65 63, respectively. Theordinates 65 64 and 65 66 correspond to the magnetic force due to thecoil 43 alone when the current through the coil 44 is Zero. Itsimultaneously follows at once from the parallelogram of forces thatthemagnetic forces due to the coil 43 are givenby the ordinates 67 62, 6771, 67 70, 67 69, 67 68, Zero, 67 72, 67 73, 67 74, 67 75, 67 63,respectively. It being assumed that the magnetic force is proportionalto the current fiowing through the coil and it being remembered that thecurrent owing through the coil 43 is practically proportional to theresistance in parallel with which the coil is con nected,it will berecognized at once that the various resistances in parallel with whichthe coil 43 must in turn be connected in order that the resultantmagnetic force may take up the directions indicated by theradius-vectors represented must be proportional to the tangents of theangles 67 65 68, 67 65 69. 67 65 70, and so on, under the suppositionthat the resistance of the coil 43 is very great as compared with theseresistances. 1f the sections of the resistance 14 15 are thereforemeasured according to the abovementioned tangent law, the receiver,apart from the small error introduced by the deformation of the currentratios due to the resistance of the voltmeter-coil,and whiclnmoreover,may be reduced to any desired extent, must revolve perfectlysynchronously with and under the same angle as the lever of thetransmitter. Fig. 3 conseq uentl y graphically shows that if themagnetic resultant moves step by step through the same angle as thetransmitting-lever the resistances must be adjusted accoi-ding to theabove tangent law and that the magnetic resultant will vary very much inmagnitude with various positions of the transmitting-lever. It is ofcourse obvious that the transmitter.

above results are true only when the current flowing through the coil 44varies as described, having during a complete revolution of thetransmittinglever one positive value, one negative value, other valueZero.

It is evident that such a telegraph apparatus renders it possible forthe pointer to make a complete revolution, and after the completion ofone revolution another revolution in the same direction can beimmediately executed, it being unnecessary for the pointer to be turnedbackward first. This is of special importance if, as is almost alwaysnecessary in the case of telegraph command apparatus on ships, anacknowledgmenttransmitter must be provided, the arrangement of which isidentical with that ot' the main transmitter. In this case thetransmitter of the acknowledgment-telegraph is arranged near thereceiver of the main apparatus, and the neutral point of the same is atthe constant potential required. Four wires are therefore sucient forapparatus including an ackowledgment- That this is an advantage which isnot to be undervalued is self-evident, for any reduction of the numberof leads is desirable; but even supposing the number of leads to v bethree the important fact must be emphasized that, in the case of thepresent invention, one of thesethree leads can be connected to a iixedpoint and only two require to be connected with a sliding contact on thetransmitter, instead of it being' necessary for all three wires to beprovided with a sliding contact. This is of exceedingly greatimpor-tance when the arrangement is employed for transmitting theindications oi a compass, in which case the transmitter is consequentlya compass.

It might be pointed out that the system is defective in that thereliability of the reading, which depends upon the absolute magnitude ofthe magnetic force resultant, is dit'- ferent, as shown above with theaid of Fig. 3, for dilerent positions of the receiving needle orpointer. As is evident from the said ligure, the resultant magneticforce is in magnitude considerably smaller in the case or' the positionsof the pointer situated on the two sides ot' and in the neighborhood ot'the contact 31, in which case the magnetic force ot' the counter forcecoil is materially the stronger than in the positions of thetransmitting-lever when the latter makes contact with the contact 16 orthe contact 26, when the magnetic force of the coil 43 (thevoltmeter-coil) is a maximum on account of the current liowing throughit being a maximum. This defect can, however, be readily `overcome bysuch a graduation or variation of the current flowing through thecounterforce coil that the resultant of the magnetic force becomesuniform to any desired degree of approximation for all positions ot' theindicating-pointer. r

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Fig. 4 shows parts o atransmitter and receiver in which the current inthe counterforce coil can be given three values, not including the valueZero. One difference between the apparatus illustrated in Fig. 4 andthat illustrated in Fig. 1 is that instead of the simple arc-shapedblocks4 38 and 39 the contact-blocks 76 77 78 79 8O (corresponding tothe block 38) and the contact-blocks 81 82 83 84 85 (corresponding tothe contact-block 39) are provided. The positive lead connected with thecontact 16 is also connected with the contact-block 83, and the negativelead connected with the contact 26 is connected with the contact-block78. The res'istances 86 87 88 89 90 91 92 93 are inserted between thevarious contact-blocks in the manner indicated in Fig. 4. Then thecontact-bar 56, Fig. 2, or' the transmitting-lever (not shown in Fig. 4)makes contact with the contactblock 83, the current through thecounterforce coil is a maximum. After the bar 56 has passed from thecontact-block 83 to the block 82 the resistance 91 is inserted in the`counter-force-coil circuit. On the bar 56, passing from thecontact-block 82 to the contact-block 81, the resistance 90 is insertedin the counter-force-coil circuit. The counterforce coil consequently istraversed b v currents of four different strengths, according as thecontact-bar 56 makes contact with the blocks 83, 82, or 81 or breaks thecircuit entirely.

From the above description, which holds good for the one quadrantof thetransmitter, (indicated in Fig. 4,) the manner in which the current inthe counter-force coil is graduated or varies when the lever is in theremaining three quadrants will be readily understood.

Fig. 5 shows the manner in which the resultant or' the magnetic forcesdue to the two coils 43 44 varies for the various positions of thetransmitting-lever when the current in the counter-force coil isgraduated, so as to have four different values (including the valuezero) by means of the arrangement shown in Fig. 4. The abscissae of thepoints 68 67 72 correspond to the maximum value of the magnetic forcedue to the current in the counterforce coil. rJhe abscissae of thepoints 69 73 74 correspond to the values of the magnetic force due tosaid current after the resistance-coils 91 or 92 have been inserted inseries with the counter-force coil. The abscissae or' the points 62 7175 63 correspond to the value of the magnetic force due to the currentafter the insertion of the two coils 90 and 91 or the insertion of thetwo coils 92 and 93, and the abscissae of the points 64 and 66, whichhave the value Zero, correspond to the Zero value of the current.

It will of course be understood that in the case of apparatuscorresponding to Figs. 4 and5 the resistance 14 15 is of course notsubdivided according to the tangent law, but is graduated incorrespondence with the grad uation of the current in the counter-forcecoil.

Fig. 6 shows the manner in which the resultant of the magnetic forcesdue to the two receiver-coils varies `for various positions of thetransmitting-lever when the current in the counter-force coil isgraduated so as to have five dilferent values, (including the valueZero.) 1t will be noticed that whereas in Fig. 5 the abscissae or' thepoints 62 71 75 63 are the same in Fig. 6 the abscissze of the points 6263 are different from those of 71 75. rlhe resultant of the magneticforces may have the same magnitude for the various positions ot' thereceiving-pointer if for each quadrant the current of the counter-forcecoil has a different value for each of the contacts which the contact 55is adapted to touch. The diagram for the resultant of the magneticforces, if the right values are given to the resistances, will thenbecome a regular polygon-that is to say, the resultants are equal inmagnitude to a high degree of approximation about the wholecircumference. This equalization of the resultants is obtained in thecase or' the arrangement shown in Fig. 7, which is as follows: To eachcontact 94 94, connected with the main resistance 14 15, (shown in. Fig.1, but not in Fig. 7,) one of the contacts 954118 corresponds. Thecontact-bar 56, Fig. 2, on the transmittinglever is adapted to makecontact with these contacts 954118. Resistances 119 are connectedbetween the various contacts 95-118 in the manner shown in Fig. 7. Thetwo contacts 95 and 107 are, however, insulated from all otherconnections. The positive lead 120 is connected with the contact 113 andthe negative lead 121 with the contact 101; otherwise the arrangementshown in Fig. 7 is the same as that shown in Fig. 4, and its method ofoperation is the same with the exception that' each time that thetransmitting-lever (not shown in Fig. 7) moves from one position to thenext the current flowing through the counter-force coil, as well as thatliowing through the voltmeter-coil 43, is varied. 1f the resistanceshave their proper values, the resultant or' the magnetic forces due tothe two coils 43 44 will be constant in magnitude whatever the positionof the transmitting-lever may be. The same object instead of beingattained by providing resistances between the various contact-blocksadapted to make contact with the bar 56, Fig. 2, which resistances b vbeing inserted in series with the counter-force coil reduce the magneticforce due to the same in the desired manner, can also be attained b vconnecting the counterforce coil in parallel with sections of the mainresistance 14 15 in any suitable manner, such as that showndiagrammatically in Fig'. 8.

The arrangement shown in Fig. 8 is as :follows: The outer circle ofcontacts 94 94,

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which may be called the voltmeter-coil contacts, and the contacts95-118, which may be called the counter-force-coil contacts, arethemselves arranged in the same manner as in the embodiment shown inFig. 7. Resistances are not, however, inserted between the variouscounter-force-coil contacts; but said contacts are connected with thevoltmeter-coil contacts in the manner shown in Fig. 8. By inspectingthis figure it will be seen that each of the counter-force-coil contactsis connected with the counter-force-coil contact situated at the samedistance from but at the other side of the voltmeter-coil contact, whichis connected directly with the lead 52. Thus the contacts 107 and 95 areconnected together and also 108 with 118, 109 with 117, 110 with 116,111 With 115, and 112 with 114. The contact 113 is connected with thenegative lead 121. In Fig. 8 the connections are shown\only on theright-hand half of the transmitter. On this half the counter-forcecoilcontacts forming the quadrant of contacts 113-118 and 95 are connectedeach with that voltmeter-coil contact of the right-hand lower quadrantwhich is at a distance of ninety degrees. Correspondingly, also, on thelefthand half the counter-force-coil contacts forming the quadrant ofcontacts 101 to 107 are each connected with that voltmeter-coil contactof the left-hand upper quadrant which is at a distance of ninetydegrees. 1n this left-hand half of the transmitter thecounter-force-coil contacts are also connected in pairs similarly tothose of the right hand. Thus 106 is connected with 96, 105 with 97, 104with 98, 108 with 99, 102with 100, and 101 is connected with thepositive lead 120. In this manner also the eiect is obtained that thecurrent in the counter-force coil becomes smaller by degrees the furtherthe lever of the transmitter is moved from the' contact at practicallyzero potential connected with the lead 52 toward the contacts connectedwith the positive and negative leads 120 121, respectively. Under somecircumstances the connections in this case also can be furthersimplified by doing away with the arrangement of a special series ofcounter-force-coil contacts and by employing an auxiliarytransmitting-lever, making an angle of ninety degrees with the maintransmitting-lever, said auxiliary lever making contact with thevoltmeter-coil contacts. This arrangement, which is hereinafterdescribed with reference to Figs. 9 and l0, is of advantage when it isdesired to transmit the complete rotations of the pointer of a vane orof a clock-hand. 1f it is merely desired to indicate the position of apointer within a definite angle, one of the systems of connections shownin Figs. 1, 11, 7, or 8 can be employed. 1t may be emphasized that inthis case, as shown in Fig. 1, a bipolar field-magnet is employed on thereceiver. 1n this case one revolution of the transmitting-levercorresponds to one revolution of the receivingpointer, and each positionof the former is indicated by a similar position of the latter. 1f onthe receiver a field-magnet having two n poles be used, n revolutions ofthe transmitter correspond to one revolution of the receiver. Viceversa, if on the receiver a bipolar Held-magnet be employed and if thetransmitter, instead of having two points at zero potential and twopoints at positive and negative potential, respectively, have two npoints at Zero potential and n points at practically constant positivepotential and n at negative potential, arranged symmetrically, onerevolution of the transmitting-lever will correspond to n revolutions ofthe pointer of the receiver.

By means of the arrangements described, on the one hand, any desirednumber of revolutions of the transmitting-lever, as well as of thepointer of the receiver, are possible in both directions of rotation,and, on the other hand, variations of the potential no longer have anyappreciable effect, as the torques of the two coils of the receiver,which are equal and opposite when the pointer is in equilibrium, areequally effected by variations of the voltage as well as by variationsin the strength of the field-magnet.

From the doubly symmetrical form of the magnetic field it follows thatthe resistances must be symmetrically grouped about the contact at Zeropotential. (In Fig. 1 the contact 81.) lThe adjustment is for the restelfected empirically, as the magnitude of the separate resistances is acomplicated angle function depending on the arrangement selected forgraduating or varying the current flowing through the counter-forcecoil.

If the coils of the receiver are not placed exactly at right angles toone another, a correction is eifected by winding about one of the coilssome windings in series with the other coil, so that the resultantbecomes vertical to the other. The same expedient is resorted to if whenusing a transmitter with two contact-arms the angle between said arms isnot exactly a right angle.

A very important application of the apparatus is for the comparison ofthe readings of two different transmitters set up at a distance from onean'other at a third point common for both transmitters. This caseoccursif a ship is provided with a gyroscope in addition to the compass and itis desired to show on a suitable instrument at a determined placewhether and how much the readings of the two instruments vary from oneanother at any time, it being of course understood that if no magneticdisturbances or disturbances of any other kind are present at all timesthe gyroscope and compass should give the same reading. For this purposethe receiver is so constructed that the constant magnetic field, inwhich, as above described, the

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system of coils influenced by the transmitter rotates, is substituted bya second fixed system of coils, which is connected up exactly like thefirst. Both systems ot' coils are mechanically so arranged that theyinfluence one another magnetically. The one system of coils isinfluenced by the one transmitter, which, for example, is so connectedwith the ships compass that the transmitting-lever rotates with thecompass-needle, and the other system of coils is actuatedelectromagnetically by the other transmitter, which is attached to thegyroscope, for example. The electromagnetic actuation or' the systems ofcoils is effected in the same manner as that in which the revolublesystem of coils 43 44 is influenced by the transmitting-lever 42, asdescribed above. If now both transmitting'- levers are turned throughthe same angle, the revoluble system of coils does not rotate, as themagnetic resultant of the magnetic forces of both systems of coils aredisplaced in the same manner, and consequently no impulse adapted toproduce motion arises. If, however, the angles turned through by the twotransmitting-levers are dilerent, the resultan ts ot' the magneticforces ot' the two coils also rotate to different extents, and theresult is a Arotation of the revoluble system oi' coils, as theapparatus always so adjusts itself that both resultants of the separatesets of coils set themselves in one and the same direction. It issupposed that the electrical connections between the twotransmitting-levers and the two systems of coils are arranged in such amanner that when the two transmitting-levers revolve in the samedirection the two magnetic resultants revolve also in the samedirection. In this case the rotation of the revoluble system of coilscorresponds to the dilierence between the rotations of the twotransmitting-levers, and it is this diiierence, in general, that theobserver ought to know; but attention is directed to the fact that it ispossible to arrange the apparatus in such way that the rotation of therevoluble system of coils indicates the sum of (and not the differencebetween) the angles turned through by the two transmitting-levers. Forthat reason the electrical connections between the transmitters and thereceiver must be so arranged that if the two transmitting-levers arerotated in the same direction the magnetic resultants of the two systemsof coils rotate in opposite directions to each other. In this a1'-rangement, however, the revoluble system of coils also rotates when thetwo transmittinglevers are turned through the same angle, the rotationbeing equal to twice the angle through which the two transmitting-leversarel turned. In Figs. 9 and 10 two embodiments of such an arrangementare diagrammatically represented. Referring in the first place to Fig.9, 130 and 131 are the two transmitters the positions of the pointers orlevers of which are to be compared at a distant and one and the samespot. 132 133 are the main and auxiliary transi'nittinglevers,respectively. They are arranged at an angle of ninety degrees, and bothare adapted to make contact with the contacts 134, between which theresistances 135 are inserted in the manner indicated in the figures. Thetransmittinglevers may, for instance, be fastened one to a compass andthe other to a gyroscope, so that they may turn with these. Thetransmitter 130 is connected with the revoluble system or' coils 43 44,which is arranged as described above. The constant magnetic {ield ol thereceiver, as described in the former part ot' the specification, is,however, substituted by the system of coils 43() 440, which coils arelixed and which inliucnce the revoluble system ot' coils magnetically.-The coils 440 440 430 430 are wound upon the four pole-pieces 136 oftheannular iield-magnet137. The coils 440 440, which are connected togetherifria" ries and which electrically may be considered as the equivalentof a single counterforce coil, arel connected with the transmitter 131in the same manner as the counter-force coil 44 with the transmitter130. The two voltmeter-coils 430 430, and which areralso connectedtogether in series, are also connected with the transmitter 131 in thesame manner as the voltmetcr-coil 43 with the transmitter 130. Theembodiment shown in Fig. 10 is essentially the same as that shown inFig. 9. Nevertheless the revoluble and stationary systems of the commonreceiver are provided with ring-windings. The various parts shown inFig. 10 are indicated by the same reference-letters as similar parts inFig. 9, so that Fig. 10 will be understood without further descriptionbeing necessary. It will be noticed that in Fig. 10 the revoluble-coilsystem is connected with the transmitter 131 and the iiXed-coil systemwith the transmitter 130.

VhatI claim as my invention, and desire to secure by Letters Patent, is-

1. In an electric-telegraph apparatus, the combination of a magnetproducing a magnetic field, two rigidly-interconnected coils, having'magnetic axes inclined to one another, revolubly mounted in said lieldand forming with the latter a receiver, a transmitter comprising' meansadapted to vary the potential of the one end of each coil, and means'for maintaining the other end of each coil at a substantially constantpotential of a magnitude between the maximum and minimum Values of thepotentials of the other ends, substantially as and for the purpose setiorth.

2. In an electric-telegraph apparatus, the combination ot a magnetproducing a magnetic iield, two rigidly-interconnected coils havingmagnetic axes inclined to one another, revolubly mounted in said iieldand forming with the latter a receiver, an electric circuit IOO IIS

comprising an electric generator and a resistance, means for maintainingthe one end of each coil and one point of the resistance atsubstantially the same potential, means for electrically connecting theother end of one coil with various parts of the resistance, and meansfor varying the potential of the other end of the other coil,substantially as and for the purpose set forth.

3. In, an electric-telegraph apparatus, the combination of a magnetproducing a magnetic field, two rigidly-interconnected coils, havingmagnetic axes inclined to one another, revolubly mounted in said fieldand forming with the latter a receiver, an electric circuit comprisingan electric generator and a resistance, means for maintaining the oneend of each coil and one point of the resistance at substantially thesame potentiahand means for electrically connecting the other end of thetwo coils with various parts of the resistance, substantially as and forthe purpose set forth.

4. In an electric-telegraph apparatus, the combination of a magnetproducing a magnetic field, two rigidly-interconnected coils, havingmagnetic axes inclined to one another, revolubly mounted in said fieldand forming with the latter a receiven'an electric circuit comprising anelectric generator, a resistance composed of a plurality of sections,and a plurality of contacts arranged in a circle and electricallyconnected with said sections, two revoluble arms adapted to make Contactwith said contacts, the one arm being at an angle of approximatelyninety degrees to the other arm, means for maintaining the one end ofeach coil and one point of the resistance at substantially the samepotential, and means electrically connecting the other ends of the twocoils with the two arms respectively, substantially as and for thepurpose set forth.

5. In an electric-telegraph apparatus, the combination of a receivercomprising a fieldmagnet, two coils on said field-magnet adapted toproduce magnetic fields having axes inclined to one another, an armaturerevol-ubly mounted in the field of the field-magnet, and two coils onsaid armature having' magnetic aXes inclined to one another: twotransmitters; means connecting one transmitter with the field-magnetcoils and means connecting the other transmitter with thearmature-coils; each transmitter comprising` means adapted to vary thepotential of the one end of each of the coils with which it isconnected, and means for maintaining the other end of each coil withwhich it is connected at a substantially contact potential of amagnitude between the maximum and minimum values of the potentials ofthe other said ends of the coils with which it is connected,substantially as and for the purpose set forth.

In testimony whereofl I have signed my name to this specification in thepresence of two subscribing witnesses.

HANS USENER. Vitnesses:

JULIUs RorKn, CARL FUHLJAHN.

